The present invention relates to a combination orthodontic bracket and ligating member for retaining an archwire or retainer wire in an archwire slot of the bracket.
Ligation of an archwire to an orthodontic bracket is one of the most time consuming and frequently repeated procedures that is practiced during orthodontic treatment. Ligation typically has been performed using elastic xe2x80x9cOxe2x80x9d rings or soft stainless steel ligature ties. The placing and removing of xe2x80x9cOxe2x80x9d rings and ligature ties are time-consuming and tedious tasks which increase patient chair side time and expense. In general in these procedures the archwire is first inserted into the archwire slots of the brackets, which are already fixed to the teeth. The archwire is then persuaded into the slots by placing the ligation member over the archwire and engaging one or more tie wings to thereby securely hold the archwire in place. The ligature is intended to continuously force the archwire to the bottom of the slot.
In various types of brackets it is the bottom of the slot which is configured to align the teeth in their correct position along the continuous length of the archwire. Hence, if the ligature does not continuously force the archwire to the bottom of the slot, the alignment of the teeth may be compromised. One drawback of elastic xe2x80x9cOxe2x80x9d rings is that they tend to lose their elasticity in a very short period of time, so that the force needed to secure the archwire in the bottom of the slot is no longer present. Thus, the archwire is able to rotate or move within the slot, resulting in an undesirable alignment. To avoid this result, elastic xe2x80x9cOxe2x80x9d ring ligatures must be replaced quite frequently. Similarly, soft stainless steel ligature ties tend to rapidly lose their retentive forces on the archwire and also must be replaced frequently.
Alternatively, there are various bracket designs that have attempted to eliminate the need for a ligature altogether. For example, xe2x80x9cActivaxe2x80x9d produced by A Company, xe2x80x9cSpeedxe2x80x9d and xe2x80x9cEdgelockxe2x80x9d produced by Ormco Corporation, and others are typical examples of ligature-less brackets that are commercially available. All of the above examples, although facilitating orthodontic procedures, have compromised certain design features of the bracket. For example, slot cavities have been designed to have a certain fixed size that is necessarily greater than the largest possible orthodontic wire commercially available; self ligation features add to the overall height of the bracket, making it more uncomfortable for the patients; and the locking mechanisms in the self ligation systems often significantly limit the possibility of providing other desirable features, such as hooks, on the bracket.
Therefore, what is needed is a self-ligating bracket which overcomes the various drawbacks mentioned above and provides sustained archwire-retaining forces during the course of orthodontic treatment.
In its broadest aspects, the present invention provides an orthodontic bracket having a ligating member containing at least one coil spring segment, in which the ligating member is configured to continuously force an archwire or retainer wire to the bottom of the slot. This results in a smaller, more comfortable bracket that may be quickly ligated and may include additional features, such as hooks, if desired. To this end, and in accordance with the principles of the present invention, the bracket body has a mesially-distally extending slot for receiving an archwire or retainer wire and includes a ligating member that forms a closed loop and contains a coil spring segment. The coil spring section of the ligating mechanism provides extension so that the ligating member may be stretched over the tie wings and the archwire or retainer wire. Subsequent to ligation, the coil spring segment will provide a continuous force that keeps the archwire or retainer wire in the bottom of the slot. Thus, the alignment of the teeth will not be compromised by rotation of the bracket due to a loosely retained archwire or retainer wire.
A further advantage of the invention is that the self ligating mechanism does not add considerably to the overall height of the bracket. Thus, patient comfort is maintained. Furthermore, the configuration of the ligating mechanism does not prevent the inclusion of other design features, such as hooks, on the bracket body. Yet another advantage is that the invention is suitable for both lingually- and labially-applied brackets.
A further advantage of the present invention is that the coil spring segment of the ligating member may be two coils wound in opposite directions such that the ends of the ligating member engage the bracket in the same plane of space.
Yet another advantage of the present invention is that a ligating member with improved fatigue resistance is provided by using a coiled, multiple stranded wire for all or a portion of the ligating member.
By virtue of the foregoing, there is thus provided a smaller, more comfortable orthodontic bracket having one or more tie wings, additional features, such as hooks, if desired, and a self ligating member containing at least one coil spring segment that may be quickly stretched over the archwire or retainer wire and tie wings, and which continuously forces the archwire or retainer wire to the bottom of the slot.
These and other objects and advantages of the present invention shall become more apparent from the accompanying drawings and description thereof.